January 8, 2015

If you are lucky in life, there is at least one person who will always be there for you—a parent, your spouse, maybe even your pooch. As we understand more and more of what goes on inside a cell, it has become clear that actin is always there for the cell’s many organelles. Actin is so supportive and encouraging, and without it our cells would just be puddles of fats and proteins. Today’s images are from a paper describing the role of actin in mitochondrial fission. 

Mitochondria are dynamic organelles that divide by fission. Although a role for the actin cytoskeleton in mitochondrial fission has been suggested, the exact mechanism is unclear. Recent work by Li and colleagues shows a transient association of F-actin (filamentous actin) to mitochondria at the start of fission. Downregulation of the actin regulators cortactin, cofilin, and Arp2/3 caused elongation of mitochondria. Li and colleagues tested the role of Drp1, which is a key player in mitochondrial division, on F-actin assembly during fission. Drp1 inhibition prolonged the localization of F-actin and several actin regulators at mitochondria during fission. In the left group of images above, F-actin (green) and mitochondria (red) are visible in a control mammalian cell (bottom row is at higher magnification). The group of images on the right shows mammalian cells after chemical induction of mitochondrial fission: 2 minutes after drug treatment, many F-actin-rich mitochondria are visible.

Li, S., Xu, S., Roelofs, B., Boyman, L., Lederer, W., Sesaki, H., & Karbowski, M. (2014). Transient assembly of F-actin on the outer mitochondrial membrane contributes to mitochondrial fission The Journal of Cell Biology, 208 (1), 109-123 DOI: 10.1083/jcb.201404050